Manufacture of ground wood pulp and grinding stone therefor



Oct- 2, 1934- F. s. FARLEY 1,975,452

MANUFACTURE OF GROUND WOOD PULP AND GRINDING STONE THEREFOR Filed NOV. 23. 1932 2 Sheets-Sheet 1 IN VEN-TOR:

Hands 8 lbz ie 'y, 55m W MA? g TTORNEYS.

Oct. 2, 1934. F. s. FARLEY; 1,975,452

MANUFACTURE OF GROUND WOOD PULP AND GRINDING STONE THEREFOR Filed Nov. 23. 1932 2 Sheets-Sheet 2 Q WW N a gllll M wyg W! TNESSES: I N VEN TOR:

W I Eealzci'; S. Farley,

.which give rise to uneven wear.

atentecl Oct. 2, 1934 j UNITED STATES PATENT OFFICE Francis S. Farley, Trenton, N. J.

Application November 23, 1932, Serial No. 644,035 6 Claims. (Cl. 51-206) This invention relates to the manufacture of aqueous fiber pulp by grinding fibrous materials like wood, and to grinding stones therefor. There are various types of abrasive grinders for this purpose to which the invention is adaptable, such as magazine grinders and pocket grinders of one, two or three or more pockets, for example.

In abrasive wood-pulp-grinders, logs or billets of wood are firmly held and pressed, sidewise, against a revolving grindstone, and water is sprayed against the abrasive (peripheral) face of the stone, across its full width. The shower of water washes off and carries away the ground-off wood particles (fiber bundles, as well as indi vidual fibers and wood flour, or fines) as a pulp suspension. The washing-out action of the water retards or prevents clogging of the superficial pores or grain-interstices of the stone by the flnes,-sometimes called glazing of the stone face,and in order to do this more effectively, the water is usually sprayed against the abrasive face in a forcible needle spray. The water also serves (to some extent) to cool the stone, which tends to heat up from the friction and work of abrasion on the wood; and the stone is usually run partly immersed in a pool of the aqueous pulp produced by it, to increase the cooling eifect. However, the cooling realized is very poor, owing to limited area of contact of the water and pulp with the stone, so that the stone tends to heat up unevenly and objectionably: i. e., the outer portionrof the stone heats more than its inner portion, giving rise to internal stresses and strains that may sometimes result in disintegration.

Such heat effects are more serious in artificial or manufactured stones than they are in natural stones, for the latter are much more capable of adjusting themselves to internal variations of temperature. However, artificial stones are superior in many other respects: they can be made more uniform in grain size, strength, porosity, hardness and general structure; whereas natural stones have a grain due to the natural processes 'of their formation, generally wear down more rapidly, and are likely to have soft spots In practice, artificial stones are commonly made of a number of arcuate segments cemented or otherwise secured together.

I have found that objectionable heating of.

suspend the fiber particles (commonly termed water for dilution) through pores in the stone during the grinding operation. Many natural and artificial stones now on the market have sufiicient permeability to permit this. Moreover, the permeability of artificial stones to water can be controlledv and varied in the process of manufacture, more or less independently of their (superficial) porosity and grain size; since permeability depends on the proportion of continuously open pores and the proportion of binder to abrasive grains. The amount of water passing through a stone of grain sizeand porosity best suited for any particular grinding work can be varied and controlled by proper predetermination of its permeability.

While all the water for dilution can be passed through the stone, it is also generally practicable to supply only enough to control the stone temperature in this way, and to introduce the rest in any well-known or desired manner, as by spraying on the acting surface of the stone as mentioned above. This affords considerable flexibility in operation; so that it is only necessary to design stones to pass the maximum ever necessary for proper cooling, without regardto' the consistency of the pulp to be made (which may ordinarily vary between 3% and 6% of fiber by weight, reckoned on a bone-dry basis). Moreover, it is sometimes desired to use so-called white water (carrying fine particles of fiber,

at a consistency of about 0.05 to 0.12% or higher) I for dilution; and this white water can be introduced by externally spraying it on the stone, while the water passed through the stone may be pure fresh water, free from fiber or other objectionable matter in suspension. However, white water can be passed through the stone (instead of fresh water), if desired.

Various methods of passing the water through a stone may be employed, such as introducing it under any desired pressure through a hollow revolving shaft into the usual central cavity of the stone, or supplying it through a stationary pipe into an annular channel connected to such cavity. With stones of such grain size and porosity as usually used for pulp-wood grinding (e. g., 60

grit), however, no external pressure to force the pulp through the pores of the stone is usually needed,centrifugal force due to the usual rapid rotation of the stone (e. g. 200-260 R. P. M. for a 54 in. diameter stone) being sufiicient. Moreover, it is not necessary that the entire radial width of the stone be traversed by the water, but only the outer peripheral portion of the stone, at whose surface the heat of abrasion is generated; and

hence the water may be so supplied as to enter the pores ,at an intermediate point or zone in the radial width of the stone, as hereinafter shown and described.

In the drawings, Fig. I is a side view, partly in elevation and partly in section, of a three -pooket construction, comprising a stone 10 mounted fast on a shaft 11 and revolving in a housing formed by base 12 and side plates (not shown) connected by cross braces or bridge trees 13, with pockets 14 between the bridge trees 13 secured to'them by bolts 15. Over each pocket 14 is mounted a hydraulic cylinder 16 containing a piston (not 7 shown) which is connected by a piston-rod 18 to a pressure foot 19 in the pocket. Each cylinder 16 has a reversing valve 20 controlling admission of water pressure either above the piston to press the sticks or billets of wood W-=in the pocket 14 against the peripheral face of the stone 10; or beneath the piston to retract the pressure foot 19, to allow a new charge of wood to be put in the pocket. For the purpose of thus charging and recharging it, each pocket 14 has a sliding side wall or gate 21 that can be raised as shown at the left of Fig. I. Besides the water supplied through the stone 10 as hereinafter described, additional water (white-water or fresh water) for dilution may be sprayed on the acting stone face through one or more needle-shower pipes 22 at the leading side(s) of the pocket(s) 14. The mixture or suspension of fiber in water collects in the pit 23 beneath the stone 10, and-overflows over the dam 24 as shown. Above and behind the dam 24 is an apron-board 25 which prevents pulp from being splashed out at this point.

Except for the supply of water through the stone 10 as referred to in the preceding paragraph, all the features described therein are well known in the art.

Referring, now, also to Figs. II and III, it will be seen that the stone 10 here shown is a thick disk with a central hole for the shaft 11, on which the stone is mounted and clamped between flanges 26. These flanges 26 are pressed together on the stone by (bronze) taper-bushings 27, fitting in the tapered hubs 28 of the flanges 26 and screwed on the shaft 11 by right and left-hand threads, so arranged that in operation the resistance to turning of the stone 10 tends to tighten the bushings and flanges together on the stone, gripping it the more tightly. As indicated in Figs. II and III, the

central portions of the stone sides are conically enlarged very slightly, from 29 inward, and the inner surfaces of the flanges 26 are correspondingly concaved.

In the stone 10 are two annuiar series of holes or ducts 30. The holes 30 of these two series alternate and extend from opposite sides of the stone nearly but not quite all the way through it, and they may slope diagonally outward at an angle of some 15, for example. At each side of thestone 10 is an annular water-supply channel 32 into which the inner ends of the corresponding series of holes or ducts 30 open, this channel being preferably formed in the inner sides of the flange 26. On the outer sides of each flange 26 is an overhanging inward-lipped flange 33 affording an inward-open channel 34 around the corresponding hub 28; and this channel 34 communicates with the supply channel 32 symmetrically around the axis of revolution of the parts, through ports or ducts 35 sloping diagonaiiy outward from channel 34 to channel 32. Water is supplied to each channel 34 through one or more (five) supply pipes 36 extending into the channel 34 below the shaft 11, and discharging radially outward.

When the stone 10 is revolving rapidly, the water supplied to each channel 34 distributes itself fairly evenly around the shaft 11, and flows through the ports 35 into the supply channel 32, where any inequality of supply is equalized. Thence it flows axially and outward through the ducts 30, and from each of them diffuses outward through the pores of the stone 10, about as indicated by the line arrows in Figs. 11' and III. Throughout its course as just described, the water is powerfully impelled by centrifugal force, which increases as the water flows along each duct 30, so as to insure a substantially uniform outflow therefrom across the entire axial width of the stone 10. Every open pore in the outer portion of the stone 10 is thus traversed by the water, which diffuses out through the porous abrasive peripheral face of the stone all over it.

L Coming thus in contact with almost every grain in the outer portion of the stone 10, and especially in its peripheral zone or layer, the water cools the stone effectually, so that the stone heats up but Having thus described my invention, I claim:-

I. A revolving peripherally acting porous abrasive stone, for grinding wood in the manufacture of aqueous ground-wood pulp, provided with means for centrifugally supplying water to diffuse outward through the periphery of the stone and carry away in a suspension the ground-off wood particles; said means comprising a series of supply ducts leading diagonally outward and across through the stone, so that the increase of centrifugal force along the ducts may assure a substantially uniform supply of water thereby over the entire facial width of the stone.

2. A revolving peripherally acting porous abrasive stone, for grinding wood in the manufacture of aqueousground-wood pulp, provided with means for centrifugally supplying water to diffuse outward through the periphery of the stone and carry away in suspension the ground-off wood particles; said means comprising a series of supply ducts leading diagonally outward and across through the stone from each side thereof, so that the increase of centrifugal force along the ducts may assure a substantially uniform supply of water thereby over the entire facial width of the stone.

3. A revolving peripherally acting porous abrasive stone, for grinding wood in the manufacture of aqueous ground-wood pulp, provided with. means for centrifugally supplying water to diffuse outward through the periphery of the stone and carry away in suspension the ground-off wood particles; said means comprising a series of supply ducts leading diagonally outward and across through the stone, so that the increase of centrifugal force along the ducts may assure a substantially uniform supply of water thereby over the entire facial width of the stone, an annular supply channel connecting the inner ends of sa d du ts, and means for supp y g water to said channel substantially symmetrically distributed around its axis.

4. A revolving peripherally acting porous abrasive stone, for grinding wood in the manufacture of aqueous ground-wood pulp, provided with means for centrifuga y Supplying water to diffuse outward through the periphery of the stone and carry away in suspension the ground-off wood particles; said means comprising series of supply ducts extending into the stone from opposite sides, and so spaced as to distribute the water substantially uniformly through the internal pores of the stone, both axially and circumferentially thereof.

5. A revolving peripherally acting porous abrasive stone, for grinding wood in the manufacture of aqueous ground-wood pulp, provided with means for centrifugally supplying water to diffuse outward through the periphery of the stone and carry away in suspension the ground-off wood particles; said means comprising a. series of supply ducts extending into the stone from its opposite sides alternately.

6. A revolving peripherally acting porous abrasive stone, for grinding wood in the manufacture of aqueous ground-wood pulp, provided with means for centrifugally supplying water to diffuse outward through the periphery of the stone and carry away in suspension the ground-01f wood particles; said means comprising series of supply ducts extending into the stone from opposite sides thereof alternately; annular supply channels at the opposite sides of the stone each connecting the inner ends of alternate ducts, inwardopen annular channels at opposite sides of the stone connected to the corresponding supply channels symmetrically around the axis of the stone, and means for delivering water into said channels. I

FRANCIS S. FARLEY. 

